linux-kernel - Re: [PATCH] scripts/gen-btf.sh: fix shebang for NixOS

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Message-ID: <c8eb9347-b23c-4ad5-9555-b2a55b788dce@linux.dev>
Date: Tue, 20 Jan 2026 21:04:08 -0800
From: Ihor Solodrai <ihor.solodrai@...ux.dev>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc: Gary Guo <gary@...yguo.net>, Thomas Weißschuh
 <linux@...ssschuh.net>, Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
 Martin KaFai Lau <martin.lau@...ux.dev>, Eduard Zingerman
 <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, bpf <bpf@...r.kernel.org>,
 LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] scripts/gen-btf.sh: fix shebang for NixOS



On 1/20/26 8:52 PM, Alexei Starovoitov wrote:
> On Tue, Jan 20, 2026 at 8:50 PM Ihor Solodrai <ihor.solodrai@...ux.dev> wrote:
>>
>>
>>
>> On 1/20/26 3:54 PM, Gary Guo wrote:
>>>> [...]
>>>>
>>>> So it's trivial to put $(CONFIG_SHELL) in front of it. But then it
>>>> must be migrated to #!/bin/sh, right?
>>>
>>> Documentation/kbuild/makefiles.rst says:
>>>
>>> Make rules may invoke scripts to build the kernel. The rules shall
>>> always provide the appropriate interpreter to execute the script. They
>>> shall not rely on the execute bits being set, and shall not invoke the
>>> script directly. For the convenience of manual script invocation, such
>>> as invoking ./scripts/checkpatch.pl, it is recommended to set execute
>>> bits on the scripts nonetheless.
>>>
>>> Kbuild provides variables $(CONFIG_SHELL), $(AWK), $(PERL),
>>> and $(PYTHON3) to refer to interpreters for the respective
>>> scripts.
>>>
>>> So I suppose it would need to migate to POSIX shell...
>>
>> That's my blunder then.
>>
>> I'll send a patch tomorrow to make gen-btf.sh runnable with /bin/sh
> 
> Isn't the current patch enough?
> -#!/bin/bash
> +#!/usr/bin/env bash
> 
> I don't think all kernel build scripts are pure 'sh'.

Well, if we want to follow the makefiles.rst (and Thomas')
recommendation, which is executing the script via $(CONFIG_SHELL),
then we have to migrate to #!/bin/sh, because that's the default.

This concerns only scripts in the kernel build pipeline AFAIU.

But you may be right that this is not a strict rule, idk.
It did come up quite late on the list.